Hey Folks! All you Researchers will need to add a reply (a comment) so you can post your research here in my blog. Learners are also allowed to reply, but your main job is to learn from the information posted by the Researchers. On Monday we will have a class discussion in which you teach one another about the content you have learned here. Learners won't know which topic is theirs until Monday, so be prepared!

OK... So our first try using the Fishbowl Structure was not exactly a great success. It was obvious who had done their research and come prepared for class. We also had some impressive diagrams to supplement the discussion. Researchers did a nice job of summarizing information for their topics and breaking it down for us.Here's what we can do better for next time:Learners need to assimilate and synthesize information, not just give an oral report. Researchers need to be faster to post info for the learners and the chat needs to focus on CONTENT, not playing around. We were not very successful in demonstrating much depth of knowledge and it's obvious that there's lots to review before Friday. It's time to stop reading about Chemistry and start understanding Chemistry -- think for yourself and look for connections and relationships. Put on your big boy/girl pants folks! We will switch roles next time and I think now that we know how it works, it will go better.

Fishbowl Research: Law of Multiple Proportions & Law of Conservation Of Mass

To put it simply, the Law of Conservation of Mass, also known as the Law of Conservation of Matter, states that matter can be neither created nor destroyed. In more scientific terms, it states that the total mass of materials present after a chemical reaction is the same as the total mass present before the reaction. Although we normally associate this law with postulate 3 (atoms of an element are not changed into atoms of a different element by chemical reactions; atoms are neither created nor destroyed in chemical reactions) of Dalton’s atomic theory, it was first stated as a physical theory by Russian scientist Mikhail Iomonosov in the year 1748. It was then confirmed by French scientist Antoine Lavoisier in 1789 when he carried out a number of carefully measured experiments in which tin and lead reacted with oxygen. It was only after this that Dalton adopted it into his laws of atomic theory. This law is often applied to basic chemical reactions and it explains what happens on an atomic level during a reaction. This law laid the foundation for many other discoveries, including the rest of the conservation laws that unite the physical sciences and explain the properties of a variety of movement and energy.

The Law of Multiple Proportions is one of the basic laws of stoichiometry. It was discovered by the English chemist John Dalton in 1804, which is why it is sometimes called Dalton’s law. He theorized that if two elements (A and B) combine to form more than one compound, the mass of (B) that can combine with a given mass of (A) are in the ratio of small whole numbers. One example of this is carbon monoxide. The mass of carbon (14) and the mass of oxygen (16) form a rough 1:1 ratio, just like the composition of the compound. Likewise, carbon dioxide forms a one to two mass ratio because the mass of one mole of carbon is 14 and the mass of two oxygen atoms is 32. John Dalton proposed this law after he carefully studied the actual numerical values of the proportions Joseph Proust had proposed in the law of definite proportions (elements combine to form compounds in certain well-defined proportions rather than mixing in any random proportion). This was an important step towards the atomic theory because it laid the basic foundation for chemical formulas and compounds. It allows us to compare the masses of substances in reactions with the masses of products and find that substances combine in particular proportions of mass.

My sources for these two topics include:
http://en.wikipedia.org/wiki/Law_of_multiple_proportions,
http://www.ehow.com/about_4568411_law-conservation-mass.html, as well as our AP Chemistry textbook on pages 38-39

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Miss Gray

8/5/2011 03:11:09 pm

You set a high standard, Megan! Thanks for getting this posted in time for your learners to do their part.

Reply

Lauryn Klein

8/6/2011 06:44:46 am

Fishbowl: The Cathode Ray Tube

The Cathode Ray Tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to create images in the form of light emitter from the fluorescent screen. The image may represent electrical waveforms (oscilloscope) pictures (television, computer monitor) radar targets and others.
The first cathode ray tube scanning device was invented by the German scientist Karl Ferdinand Braun in 1897. Braun introduced a CRT with a fluorescent screen, known as the cathode ray oscilloscope. The screen would emit a visible light when struck by a beam of electrons.
In 1878, an Englishmen, Sir William Crookes, was the first person to confirm the existence of cathode rays, streams of electrons, by displaying them, with his invention of the Crookes tube, a crude prototype for all future cathode ray tubes.
By the 1870s, British physicist Sir William Crookes and others were able to evacuate tubers to a lower pressure, below 10−6 atm. These were called Crookes tubes. Faraday had been the first to notice a dark space just in front of the cathode, where there was no luminescence. This came to be called the “cathode dark space”, “Faraday dark space” or “Crookes dark space”. Crookes found that as he pumped more air out of the tubes, the tube was totally dark. But at the anode (positive) end of the tube, the glass of the tube itself began to glow.
What was happening was that as more air was pumped from the tubes, the electrons could travel farther, on average, before they struck a gas atom. By the time the tube was dark, most of the electrons could travel in straight lines from the cathode to the anode end of the tube without collision. With no obstructions, these low mass particles were accelerated to high velocities by the voltage between the electrodes. These were the cathode rays.
When they reached the anode end of the tube, they were travelling so fast that, although they were attracted to it, they often flew past the anode and struck the back wall of the tube. When they struck atoms in the glass wall, they excited their orbital electrons to higher energy levels, causing them to fluoresce. Later researchers painted the inside back wall with fluorescent chemicals such as zinc sulfide, to make the glow more visible.
In 1897, a German, Karl Ferdinand Braun, invented the CRT oscilloscope- the Braun Tube was the forerunner of today’s televisions and radar tubes.
In 1907, the Russian scientist Boris Rosing (who worked with Vladimir Kosma Zworykin) used a CRT in the receiver of a television system that at the camera end made use of a mirror-drum scanning. Rosing transmitted crude geometrical patterns onto the television screen and was the first inventor to do so using a CRT. Which marked the first time that CRT technology was used for what is know known as television.
In 1929, Vladimir Kosma Zworykin invented a cathode ray tube called the kinescope- for use with a primitive television system.
In 1931, Allen B. Du Mont made the first commercially practical and durable CRT for television.
Besides television sets, cathode ray tubes are used in computer monitors, automated teller machines, video game machines, video cameras, oscilloscopes and radar displays.
The cathode rays (electrons) originate from the negative plate on the left and are accelerated toward the positive plate, which has a hole in its center. A beam of electrons passes through the hole and in the deflected by the magnetic and electric fields. The three paths result from different strengths of the magnetic and electric fields. The charge-to-mass ratio of the electron can be determined by measuring the effects that the magnetic and electric fields have on the direction of the beam.

Dalton
John Dalton was born September 6, 1766 and died July 24, 1844. Dalton began teaching at a very young age until he began to study meteorology. While studying, Dalton came up with his Law of Partial Pressure. This states: “If two or more non-reacting mixtures of gases are enclosed in a vessel, the total pressure exerted by them is equal to the sum of their partial pressure”. A mathematical representation of Dalton’s Law of Partial Pressure is: Ptotal = Pa + Pb + Pc…etc. In terms of Kinetic Molecular Theory, Dalton’s law of Partial Pressure explains that the total pressure exerted by the gaseous mixture is equal to the sum of collisions of the molecules of individual gas.
After coming up with his partial pressure theory, Dalton began coming up with his own atomic theory. Although there were theories that were proposed by Democritus and Aristotle, the first accepted theory was proposed by Dalton. Dalton’s atomic theory consisted of the following:
• All elements are made up of tiny indivisible particles, known as atoms
• Atoms of the same element are identical with respect to their weights
• Atoms of different elements are different from each other and can be identified by their relative weights
• Atoms can neither be divided into smaller particles nor destroyed
• Chemical reactions occur due to the rearrangement of the atoms
• Atoms combine in the ratio of whole numbers such as 1:1, 1:2, 2:3 etc.
• Atoms of two or more different elements combine together to form chemical compounds.
Dalton’s theory explained several laws including the law of constant compositions: In a given compound, the relative numbers and kinds of atoms are constant. Dalton’s theory also talked about the law of conservation of mass: The total mass of materials present after a chemical reaction is the same as the total mass present before the reaction. Dalton’s theory is also a great one since it states a new theory, the law of multiple proportions (I would go into detail about this one but Megan already explained it in her fishbowl topic).
Dalton reached his conclusion about atoms on the basis of chemical observations in his laboratory. When he published his works, he did so without evidence and relied completely on suspicion and faith. Although the main principles of Dalton’s theory were correct, there were some flaws that were later revealed. These flaws include that atoms cannot be subdivided, created, or destroyed into smaller pieces. Atoms can in fact do this with the existence of nuclear fusion and nuclear fission. Another flaw to Dalton’s theory was that all atoms of a given element are identical in their physical and chemical properties is not exactly true. We know that there are isotopes of different elements which differ vaguely from each other in their mass.
All in all, Dalton’s theories have helped scientists progress further in finding more and more about atoms. His theories are still taught to this day and he is considered by all to be the father of modern atomic theory.
http://isaacmmcphee.suite101.com/john-dalton-and-atomic-theory-a45450.html
http://www.chemheritage.org/discover/chemistry-in-history/themes/the-path-to-the-periodic-table/dalton.aspx
http://en.wikipedia.org/wiki/Dalton%27s_atomic_theory#Atomic_theory

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Miss gray

8/6/2011 10:58:10 am

thank you Zach! Good summary

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Cameron Peaslee

8/7/2011 02:36:42 am

Fishbowl: Oil Drop Experiment

The oil drop experiment was an experiment performed by Robert Millikan and Harvey Fletcher in 1909 to measure the elementary electric charge (the charge of the electron). During the experiment they had to balance the downward gravitational force with the upward electric forces on tiny droplets of oil suspended between two metal electrodes. As they repeating the experiment for many droplets, they had confirmed that the chargers were all multiples of some value, even if a very small value.
Method: The oil drops are allowed to fall between the plates with the electric field turned off. They reach a terminal velocity because of friction with the air in the chamber. When the electric field is turned on the charged oil drops with start to rise. A drop is then chosen and kept in the middle of the field (by switch on and off the voltage) until all other drops have fallen. The drop is allowed to fall and its terminal velocity is calculated.
Millikan had many fraud allegations about his second experiment by Ferald Holton. Holton had said "that Millikan disregarded a large set of the oil drops gained in his experiments without apparent reason." David Goodstein says that Millikan states that he only included drops which had undergone a "complete series of observations" and excluded no drops from this group.

Earnest Rutherford was a New Zealand scientist born on August 30, 1871. Because of his findings in the atom's structure, he is known as the father of nuclear physics. At the time of Rutherford's Gold Foil Experiment, the popular atomic theory was J.J. Thompson's Plum Pudding Model. Thompson's theory suggested that negatively charged electrons, and positively charged neutrons floated together in the same area of the atom. Thompson's theory was the most common atomic theory, until Rutherford disproved it with his Gold Foil Experiment in 1911. Rutherford developed the theory that we use today, after his findings in the Gold Foil Experiment. Rutherford's theory stated that the atom consisted of a central positive nucleus with negative electrons orbiting around the nucleus. Rutherford’s model suggested that the nucleus contained most of the mass, and the remaining part of the atom was essentially empty space. In his Gold Foil Experiment, Rutherford fired radioactive particles through thin metal foils (gold, hence the title of his experiment.) Then he detected the particles using screens coated with zinc sulfide. He found that while most of the particles passed straight through the foil, about 1 in 8,000 did not. This lead to Rutherford’s theory that majority of the atom was made up of empty space.

Nice work Cameron. The Oil Drop Experiment established fundamental charge -- this is a key to solving many problems!

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Miss Gray

8/7/2011 06:15:47 am

Good job, Tara. Rutherford's work caused a revolution in how matter is percieved -- mostly empty space! Who would think that looking at a person, you're really seeing empty space. Gives new meaning to the term "Airhead" doesn't it!

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Derek Marvin

8/7/2011 07:31:22 am

Fish Bowl: J. J. Thompson
Joseph John "J. J." Thomson (December 18th,1856 – August 30th,1940) is most known for the discovery of the electron and of isotopes.
Electron
In 1897, he was the first to propose that there was a smaller unit 1,000 times smaller than an atom (suggesting the existence of sub-atomic particles). He thought of this through his explorations on the properties of cathode rays. He estimated the mass of cathode rays by measuring the heat generated when the rays hit a thermal junction and comparing this with the magnetic deflection of the rays. This experiment suggested that cathode rays were 1,000 times lighter than the hydrogen atom, and that their mass stayed the same (no matter what atom they came from). He said that the rays were composed of very light, negatively charged particles, which were named "corpuscles", which were essential to the make of atoms. Later scientists preferred electron as the name. To explain the overall neutral charge of the atom, he proposed that the "corpuscles" were arranged in a uniform sea of positive charge (although in Thomson's model they did not stay still, but orbited rapidly).
Isotopes
In 1912 (25 years after he discovered electrons) in Thompson's work into the make of canal rays, he and his research assistant, channelled a stream of ionized neon through a magnetic and an electric field and measured its deflection by placing a photographic plate in its path. They saw two patches of light on the plate, which would suggest two different parabolas of deflection. This said that neon is composed of atoms of two different atomic masses. This was the first evidence for isotopes of a stable element. His separation of neon isotopes by their mass was the first example of mass spectrometry.

Born in Copenhagen, on October 7, 1885. Bohr was a Danish physicist who made fundamental contrubutions to understanding atomic structure and quantum mechanics; in which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in Copenhagen; he was a part of a team of physicists working on the Manhattan Project. Bohr has been described as one of the most influential scientists of the 20th century.

Bohr's contributions to Physics and Chemistry
1.The Bohr model of the atom, the theory that electrons travel in discrete orbits around the atom's nucleus.
2.The shell model of the atom, where the chemical properties of an element are determined by the electrons in the outermost orbit.
3.The correspondence principle, the basic tool of Old quantum theory.
4.The liquid drop model of the atomic nucleus.
5.Identified the isotope of uranium that was responsible for slow-neutron fission – 235U.[21]
6.Much work on the Copenhagen interpretation of quantum mechanics.
7.The principle of complementarity: that items could be separately analyzed as having several contradictory properties

Reserachers: Please click the link to get to the chatroom for the fishbowl

Reply

Miss Gray

8/8/2011 02:30:46 am

OK, I didn't expect that... the link is active if you click on my name, Miss Gray, in the post above. Wierd...

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Miss Gray

8/8/2011 01:17:26 pm

Go to the AP Chemistry Section and you'll find our chat saved in Unit One. For our first time using the Fishbowl Structure, it was not too bad, but definitely not a fantastic success either. We will get better!
Thoughts to consider for next time:
Researchers, it would be helpful to post your information as soon as possible so Learners have time to study it more thoroughly. You all did a good job of summarizing, but some of the important details were left out. During the chat, your focus needs to be CONTENT, not playing around.
Learners, please work to assimilate and synthesize information, not just repeat it as an oral report. A discussion is not a bookreport. In this class, you all need to collaborate, create, and contribute -- no hiding!
ALL: Look beyond the text. Stop reading about Chemistry and work to UNDERSTAND Chemistry. Look for connections and relationships between ideas. The next time we do this, the roles will switch and we will all have a better idea of how this structure works so it will be better.
Overall, our class demonstrated a lack of in-depth understanding of Atomic Theory and you'll have a lot to review before your test on Friday. You know where to find me if you need to study!